Does Google know too much about you?

Google's linked data policy, which came into effect on March 1, allows the company to collect information about its users across all its products, services and websites and store it in one place. This has been criticised by organisations ranging from CNIL to Microsoft, all of whom have expressed concerns that it's difficult to tell which data Google collects and how it's used. Now the Information Commissioner's Office is investigating whether Google's privacy policy is compliant with UK law. Are you worried that Google knows too much about you?